Scientists were excavating a site in Laetoli, Tanzania when they uncovered two new sets of hominin tracks located about 150 meters south of the tracks found by Mary Leakey in the 1970’s. They estimated the heights of the two individuals using the size and shape of the footprints.

In this study, scientists compared two populations of pregnant mice, one which was kept germ-free throughout pregnancy and the other which was exposed during pregnancy to a strain of E. coli to determine whether the immune systems of offspring begin to develop in utero. Worksheets also available in Spanish.

Scientists collected bacteria from locations that had never been exposed to humans or modern antibiotics to determine if antibiotic resistance is newly evolved since the introduction of antibiotics or has evolved independently.

Cancer is typically attributed to hereditary and environmental factors, but these only explain a fraction of overall cancer risk. In this study, researchers investigated how a third factor—chance genetic mutations that occur during stem cell division—may contribute to the overall rate of cancer incidence in different body tissues.